<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>左上角</title>
    <style type="text/css">
    .box{
        width: 105px;
        height: 105px;
        background-color: #e7e7e7;
        border-radius: 5px;
        padding: 5px;
        margin: 5px;
        display: flex;
        align-items: center;
        justify-content: center;
    }
    .item{
        width: 26px;
        height: 26px;
        border-radius: 13px;
        background-color: black;
    }
    </style>
</head>
<body>
    <div class="box">
        <div class="item"></div>
    </div>
</body>
</html>